Dust distribution in circumstellar disks harboring multi-planet systems. II. Super-thermal mass planets

Abstract

Theoretical formation models and exoplanet detection surveys indicate that systems with multiple giant planets are common. We investigate how multiple super-thermal mass planets embedded in a circumstellar disk shape the dust distribution and examine the consequences for interpreting disk substructures and inferring planetary properties. We perform two-dimensional hydrodynamical simulations with a modified PLUTO code, treating dust as Lagrangian particles in a wide range of sizes. We analyze systems with two planets of different masses and orbital separations, comparing them to the single-planet scenario. We generate synthetic ALMA continuum maps using RADMC-3D and compute the relative impact velocities of dust particles to assess potential limitations to grain growth. Dust morphologies in multi-planet systems cannot be described as a simple superposition of single-planet gaps. Secular planetary perturbations can generate multiple dust traps and asymmetric structures, while also exciting significant eccentricities in dust particle orbits. As a consequence, the locations and widths of dust rings and gaps depend on the size of the particles, the masses of the planet, and the orbital configurations. Synthetic continuum images may hide gaps carved by multiple planets, thereby complicating the interpretation of observed substructures. In addition, eccentricities induced in dust orbits lead to stronger gas drag, reducing the Stokes number for a given particle size, and the enhanced relative velocities associated with eccentric orbits can further suppress grain growth, promoting fragmentation and replenishment of small dust grains.

Figures (8)

• Figure 1: Dust distributions for three representative grain sizes. From left to right: 100 $\mu$m, 1.6 mm, and 2.6 cm particles. Rows correspond to different planetary configurations: single planet (top), two Jupiter-mass planets on close orbits (second), two Jupiter-mass planets on wide orbits (third), and a Jupiter–Saturn pair on wide orbits (bottom). The black dashed curve shows the radial gas surface density profile (normalized between 0 and 2$\pi$). Green filled circles mark the planet locations.
• Figure 2: Radial distribution of dust particle number density for each model, computed in radial bins of 0.25 au. Black, red, and blue lines correspond to 100 $\mu$m, 1.6 mm, and 2.6 cm particles, respectively. Orange filled circles mark the planet locations. Top left: single planet. Top right: two Jupiter-mass planets on close orbits. Bottom panels: wide-orbit configurations.
• Figure 3: Dust particle orbital eccentricity versus radial distance for each model. Green filled circles mark planet locations. Colored points denote grain sizes of 100 $\mu$m (green), 1.6 mm (cyan), and 2.6 cm (magenta).
• Figure 4: Gas and dust distributions for two widely separated Jupiter-mass planets. Blue dots represent 1.6-mm dust particles, superimposed on the perturbed gas surface density $\Delta \Sigma / \Sigma _0$ (color scale). Green (yellow) dashed lines indicate the 2:1 (3:2) mean motion resonance with the outer planet. The plot is zoomed in the region between 15 to 35 AU to better visualize the dust overdensity near the outer gap edge.
• Figure 5: Dust continuum emission convolved with a realistic ALMA beam in Band 7 (first row), Band 6 (second row) and Band 3 (third row). Columns correspond to the models CloseJup (left), WideJup (middle), and WideSat (right). Bottom panel: radial intensity profiles in Bands 7 (brown), 6 (orange), and 3 (yellow), together with dust (blue dashed) and gas (black dashed) radial profiles. Cyan crosses and green filled circles mark the planet locations.